I guess it's just an omission. I only tested in FR and EU codes but as all latest samsung mp3 players have this with any code except KR, there's no reason the U5 is different. Unfortunately I don't have a U5 anymore to check...

"US samsung support product specialist"
Let me laugh If there is a Samsung Expert somewhere, that would rather be me for instance...
All U5 are the same. There is no US model particularly.
Only region code changes. So if he has a KR region code, that's normal there is no "pc connection" option because it is only UMS
I reviewed the U5 and I changed several times the region code with the famous easy config.dat trick that works with any Samsung mp3 player. And there is this option with FR and EU region code. And most likely with US region code too. And if ever there isn't this option with the US region code, you can change it into EU to get it..
So there is absolutely no reason to doubt

edit:
I just checked the US website:
"OS Compatibility MTP: Windows Vista or XP, WMP10 or higher
UMS: Windows Vista or XP or 2000 USB Connection(MTP/UMS) Yes "
So so...I hope your "Samsung specialist" is not well paid for his poor knowledges lol

So so...I hope your "Samsung specialist" is not well paid for his poor knowledges lol

US Samsung support has 3 tiers, the first 2 are useless and don't even have access to the players they support. The 3rd one, called "product specialist" is more technical and they have the devices. The guy in the 3rd tier I spoke to, claimed to have a u5 in his hands as he was double checking the system menu while on the phone with me. I have no reason to think he was lying, so it looks like the US region code hides the connection option.

Can you please post directions (or a link) for changing the region code for the U5.

What I already told twice is that he doesn't have necessarily a US region code on his U5. That can be KR. I'm in touch with Samsung France, particularly with the technical support and I know what mp3 players they have. Usually, Samsung KR only send samples to its subsidiaries. So he doesn't necessarily have a commercial version of the U5 with US region code, the one you find in stores in the USA.
So it's not a question of lying or not, it's a question of knowledges.
I give you a good answer for free. That's his job, he is paid for that and it looks like he doesn't know so much about his products.

It seems that on the newest models there is no risk. I changed the region code without updating the firmware on P3, Q2, U5, R1... and I never had this problem.
But once again, I'm convinced you even won't have to change the region code

Actually, you cannot change the MTP/UMS entry in the config.dat. Every region has its own entry.
EU/US/FR>MTP
KR/RU/CH>UMS
It corresponds to the default setting.
You know, most users are not expert and don't even know what MSC/UMS and MTP stand for. So Samsung choose for them the connexion mode.
But for you, as you know you can change it in the settings, it doesn't matter if it is MTP or UMS as default setting